1. Field of the Invention
The present invention relates to an applicator for use in hyperthermia, and, more particularly, to an applicator for use in hyperthermia which is used to treat a predetermined position of a human body by locally applying heat thereto by means of electromagnetic waves. 2. Prior Art
Lately, hyperthermia has been attracting attention. Recent reseaches (including that reported on Page 14 of MICROWAVES, October, 1976) have shown that, if heat is continuously applied to a malignant tumor at a temperature of about 43.degree. C. for an hour or two, and this application of heat is repeated at regular intervals, it is possible to impede the regeneration of cancer cells and simultaneously kill most of them. Hyperthermia of this tyoe falls into two categories: general hyperthermia and local hyperthermia. In local hyperthermia, in which cancerous tissue and its surroundings are selectively heated, methods using electromagnetic waves, electromagnetic induction, or ultrasonic waves have been proposed.
Present inventors have proposed and are continuing to research the treantment of the cancers located deep in the human body by means of electromagnetic waves. In employing electromagnetic waves, it is necessary to focus the electromagnetic energy when transmitting the electromagnetic waves into the body. For this purpose, the present inventors have incorporated an electromagnetic lens in a heating applicator. An applicator 1 adopted by the present inventors, as shown in FIGS. 1 and 2, is composed of a casing 3 which functions as a waveguide, a wave supply portion 2 provided at one end of the casing 3, and an electromagnetic lens portions 4 provided at the other end of the casing 3. An output side of the electromagnetic lens portions 4 is provided with a solid cooling plate 5 which prevents the surface of the body from overheating, and which can be cooled by cooling water.
The electromagnetic lens portion 4 is constructed so that metal plates 6A, 6A are disposed at predetermined intervals a, as shown in FIG. 2. In order to convert spherical waves transmitted from the wave supply portion 2 into plane waves, the electromagnetic-reception edge of each metal plate 6A is concave over its entire vertical length, so that the plate outputs substantially completely plane waves. Metal plates of shorter lengths are disposed in the center portion of the array of metal plates 6A so that the entire electromagnetic-transmission sides of the array of metal plates 6A is concave in the direction which is perpendicular to the concave sides of the metal plates, as shown in FIG. 2, so as to focus one side of the plane waves which are formed by the concave edge of each metal plate.
However, this conventional applicator suffers from the following disadvantages:
(1) Since the electromagnetic waves are focused in only one direction, sufficient or efficient focusing is not available in the body.
(2) A plurality of different applicators must be provided in order to treat affected parts located at different depths. The most suitable applicator is selected from the plurality of applicators every time treatment is conducted, and it must then be mounted on a support mechanism, making the preparation time-consuming.
(3) A large number of applicators must be prepared, which makes the apparatus expensive.